This invention relates to a thermosensitive label capable of developing a number of colors.
A weighing and pricing apparatus currently in wide use operates by weighing a product by means of an electronic scale, printing such information as product name, unit price, weight and overall price on a label by a printer operatively associated with the electronic scale, packing the weighed product and then adhering the printed label to the surface of the product package.
Various labels and printers are employed in the above-described apparatus. One form of label in wide use is a thermosensitive label, which is so designed that only those portions of the label heated to a prescribed temperature of, e.g., about 80.degree. to 90.degree. C., will change color. To print characters on a thermosensitive label in accordance with the prior art, a length of strippable paper carrier having a predetermined number of the thermosensitive labels adhered thereto is loaded into a thermal printer, and the paper carrier is fed through the printer at prescribed increments. Within the printer, a thermosensitive printing head is brought into pressured contact with the thermosensitive labels adhered to the paper carrier, and predetermined ones of a multiplicity of heating elements in the printing head are momentarily heated to print the abovementioned information on the labels at designated locations.
With the foregoing conventional method, however, the label is capable of developing only a single color, such as the color black, so that certain items of printed information cannot be emphasized or made easier to read by distinguishing them from other items of information by means of different colors.
Although there has been developed a thermosensitive label capable of developing two colors such as black and red by changing the temperature of the applied heat, it is not possible to rapidly change the heating temperature produced by the heating elements of the printing head. This makes it difficult to change the color of a row of print simultaneously from one color to the other during printing. The end result is that thermoprinting is performed through use of only one color, say black or red.